Radar device

ABSTRACT

The present invention provides a radar device mounted on a moving object that moves along a continuous plane, having (1) a transceiver part for transmitting a signal having a main lobe in the direction of the movement of the moving object and a side lobe directed towards the continuous plane, that receives a first reflection signal from a target in the direction of the main lobe and a second reflection signal from the continuous plane in the direction of the side lobe, and (2) control processing means for detecting the frequency of a beat signal of the second reflection signal received by the transceiver part and the signal emitted by the transceiver part and for detecting information correlated to the attitude of the radar device with respect to the continuous plane based on that frequency. This enables detection of changes of mounting attitude for the moving object without requiring additional hardware.

TECHNICAL FIELD

The present invention relates to a radar that detects the existence of atarget by transmitting radio waves and receiving the waves reflectedfrom the target.

BACKGROUND ART

Radio radars are employed in a variety of fields for measuring thedistance to a target. For example, in the automobile manufacturingindustry, development is proceeding on radar for vehicle loading thatmeasures the distance between a forward vehicle and another vehicle.

Such radar are classified into a variety of forms depending on thewaveform of the radio waves used. In an article entitled “Current Statusand Trends of mm-Wave Automobile Radar”, on pages 977-981 of theOctober, 1996 edition, Journal of the Institute of ElectronicInformation and Communication Engineers for example, a variety of formsof radar are mentioned, including pulse radar, FSK (Frequency ShiftKeying) CW (Continuous Wave) radar and FMCW (Frequency ModulatedContinuous Wave) radar. A pulse radar is a wireless device that emitspulse waves and detects the distance to a target based on the time thatelapses until the echo waves are received. The FSK is a wireless devicethat emits each of two different continuous wave alternatively, based ona Doppler-shift of each echo thereof, and detects the distance to atarget object and the relative speed of the target object. An FMCW radaris a wireless device that emits continuous waves of a suitable repeatingfrequency modulation, such as a triangular wave frequency modulation orthe like, and detects the distance to a target object and the relativespeed of the target object based on the beat frequency of thetransmitted signals and the reflected signals. Among such radar, FSK CWand FMCW radars detect the distance to and relative speed of a targetbased on the phase and frequency of peak signals of a frequency spectralobtained by FFT (Fast Fourier Transform) processes applied to signalsreceived at a reception antenna.

First, a vehicle mounted radar is mounted on the vehicle mainly for thepurpose of detecting a target (such as a vehicle in front) that existson the surface of the road, therefore the radar may not erroneouslydetect a pedestrian bridge positioned over the road for example, as thetarget. Thus, the radar must maintain an attitude when in the conditionof being mounted on the vehicle, enabling radio waves to be transmittedto the planar direction of the road surface and radio waves to bereceived from the planar direction of the road surface. The technologydisclosed in JP-A-2000-56020 is well know in connection with suchradars. This technology provides two electromagnetic wave emittingsources for emitting electromagnetic waves in slightly verticallyinclined directions for the forward direction of a vehicle, mounted onan object detection apparatus, with changes in the attitude of theobject detection apparatus being detected by comparing the strength ofreflected waves of the electromagnetic waves from each electromagneticwave emitting source. JP-A-2000-56020 cites laser rays and milliwaves asexamples of the electromagnetic waves.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a radar device thatcan detect variation in the mounting attitude for a moving object,without adding any hardware. To achieve this objective the presentinvention provides a radar device mounted on a moving object that movesalong a continuous plane, having (1) a transceiver part that transmits asignal having a main lobe in the direction of the movement of the movingobject and a side lobe directed towards the continuous plane, and thatreceives a first reflection signal from a target in the direction of themain lobe and a second reflection signal from the continuous plane inthe direction of the side lobe, and (2) control processing means whichdetects the frequency of a beat signal of the second reflection signalreceived by the transceiver part and the signal emitted by thetransceiver part, and that detects information correlated to theattitude of the radar device with respect to the continuous plane basedon that frequency.

As much freedom as possible is maintained in the combination of partsincluded in the concrete structure proposed for the best embodiment forimplementing the present invention, the present invention comprising anysuch combination. For example an embodiment obtained by appropriatelyeliminating a part of the structure proposed for the best embodiment forimplementing the present invention may still provide an embodiment ofthis invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows antenna characteristics obtained by synthesis of antennagain of a reception antenna and a transmission antenna of a radarrelated to a first embodiment of the present invention.

FIG. 2 shows an antenna pattern illustrating a theory for detecting themounting attitude of a radar for a moving object.

FIG. 3 shows an antenna pattern illustrating a theory for detecting themounting attitude of a radar for a moving object.

FIG. 4 schematically depicts a radar system related to a firstembodiment of the present invention.

FIG. 5 illustrates the structure of the housing for a radar related to afirst embodiment of the present invention.

FIG. 6 is a flowchart depicting the processes executed by amicrocomputer related to a first embodiment of the present invention.

FIG. 7 depicts a frequency spectral generated by FFT.

FIG. 8 depicts a frequency spectral generated by FFT.

FIG. 9 is a flowchart depicting the processes executed by amicrocomputer related to a first embodiment of the present invention.

FIG. 10 shows the variation in the frequency of a transmission signalfrom an FMCW radar.

FIG. 11 shows the variation in the frequency of a beat signal obtainedby mixing a transmission signal from an FMCW radar and a reflectionsignal thereof.

FIG. 12 depicts a frequency spectral generated by FFT.

FIG. 13 is a flowchart depicting the processes executed by amicrocomputer related to a first embodiment of the present invention.

FIG. 14 is a flowchart depicting the processes executed by amicrocomputer related to a first embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiments of the present invention will now be described withreference to the drawings.

This description begins with an explanation of the theory behind thedetection of the mounting attitude of a radar for mounted on a movingobject.

As shown in FIG. 1, normally, a radar antenna is designed having aradiation pattern of radio waves in which a series of side lobes a1, a2,. . . , a1′, a2′ and . . . , continuing from a main lobe a0 arerepresented as radiation within a range of angles of ±90° extending fromthe main lobe a0. Accordingly, as shown in FIG. 2, if a radar 100 ismounted on a moving object 400 moving on a level surface 300 such thatthe main lobe a0 of the antenna and that moving object are parallel, theangles Φ1, Φ2, . . . , formed between the surface 300 and the side lobesa1, a2, . . . , that are a part of the side lobes a1, a2, . . . , a1′,a2′, . . . of the antenna, may theoretically be equivalent to the anglesø1, ø2, . . . of the main lobe a0. Hereinafter this mounting attitude ofa radar on a moving object is taken as the standard attitude. Here, if avariation arises in this mounting attitude of the radar 100 on themoving object 400 a variation correlated thereto arises in the anglebetween the surface 300 and the side lobes a1, a2, . . . of the antenna.As shown in FIG. 3 for example, if the mounting attitude of the radar100 on the moving object is rotated at an angle θ from the standardattitude around a straight axis horizontal to the forward direction ofmovement of the vehicle on which the radar is mounted, the angles Φ1,Φ2, . . . between the surface 300 and the side lobes a1, a2, . . . ofthe antenna may theoretically increase at an angle equivalent to thatangle of rotation θ of the radar.

In this way, the angle between the surface and the side lobes of theantenna varies in correlation to the angle of the rotation of the radararound a straight axis horizontal to the direction of movement of thevehicle on which the radar is mounted. According to this embodiment ofthe present invention, the angles Φ1, Φ2, . . . formed between thesurface 300 and the side lobes a1, a2, . . . of the antenna are detectedand the variation in the mounting attitude of the radar on the movingobject is estimated based on the detected results. The method forcalculating the angles Φ1, Φ2, . . . formed between the surface 300 andthe side lobes a1, a2, . . . of the antenna differs for the modulationsystem of the radar. Concrete examples of this follow.

The angles Φ1, Φ2, . . . formed between the surface 300 and the sidelobes a1, a2, . . . of the antenna for a FSK CW radar for example, canbe calculated in the following way.

If an object exists in the region of radio waves radiation from theantenna of a radar the antenna receives an echo from that object. Thisecho is subject to the Doppler effect due to the relative movementbetween the radar and the object.

Accordingly, the frequency of this echo shifts only the Dopplerfrequency f provided by expression (1) from the emitted frequency fc ofthe radio waves from the antenna.f=2·fc·v/c  (1)

Here, c is the speed of light and v is the relative speed of the radarand the object.

If static objects exist in the directions of each of the side lobes a1,a2, . . . of the antenna of a radar moving at speed V the relativespeeds of each of those static objects and the radar are V·cos Φ1, V·cosΦ2. Accordingly if the Doppler frequencies f1, f2, . . . of the echoreceived from each of the static objects by the antenna of the radar areobtained from expression (1), expression (2) is obtained.fk=2·fc·V·cos Φk/c(k= 1, 2, . . . )  (2)

If the surface existing in the directions of each of the side lobes a1,a2, . . . of the antenna when the radar is mounted on the moving objectmoving over that surface at speed V is considered to be a static objectand the Doppler frequencies f1, f2, . . . of the echoes from the surfaceare detected using FFT processes, the angles Φ1, Φ2, . . . between thesurface 300 and the side lobes a1, a2, . . . of the antenna can beobtained by substituting those detected values f1, f2, . . . inexpression (2).

Further, the angles Φ1, Φ2, . . . formed between the surface 300 and theside lobes a1, a2, . . . of the antenna for an FMCW radar for example,can be calculated in the following way.

The Range, being the distance from a radar to an object existing in theregion of radiation of radio waves from the antenna of the radar, can beobtained by expression (3).Range=c·(fb++fb−)/(8·ΔF·fm)  (3)

Here, c is the speed of light, fb++fb− is the sum of values fb+, fb−(refer to FIG. 11) alternately shown by frequencies of the beat signalof the echo from the object, fm indicates the cycles of repetition oftransmission of radio waves (refer to FIG. 10) from the transmissionantenna, ΔF is the bandwidth of the frequency deviation of radio wavestransmitted from the transmission antenna and λ is the wavelength ofradio waves from the transmission antenna.

If the surface existing in the directions of each of the side lobes a1,a2, . . . of the radar antenna is considered a static object, thedistance (R1, R2, . . . in FIGS. 2 and 3) between the radar and theposition at which each of the side lobes a1, a2, . . . from the radarantenna reach the surface can also be obtained by the Range ofexpression (3). If the distance (R1, R2, . . . of FIGS. 2 and 3) betweenthe radar and the position at which each of the side lobes a1, a2, . . .from the radar antenna reach the surface are geometrically calculatedexpression (4) is obtained.Rk=H/sin Φk(k=1, 2, . . . )  (4)

Here, H represents the distance (H of FIG. 2) between the surface andthe main lobe aO of the antenna of the radar maintaining the standardattitude.

Substituting distance Rk obtained from expression (4) for the Range ofFIG. (3) produces expression (5).H/sin Φk=c·(fb++fb−)/(8·ΔF·fm)(k32 1, 2, . . . )  (5)

Detecting the frequencies fb+, fb− shown alternately by the beat signalof the echo from the surface for each side lobe using FFT processes andsubstituting those detected values fb+, fb− in expression (5) enablesthe angles Φ1, Φ2, . . . formed between the surface 300 and each of theside lobes a1, a2, . . . of the antenna to be obtained.

A structure for a radar system capable of estimating the mountingattitude of the radar on a moving object using the above principles willnow be described. Here, a homodyne type FSK CW radar is described toprovide an example of a radar of this radar system, however this doesnot preclude usage of a heterodyne system FSK CW radar.

As shown in FIG. 4 a radar system according to this embodiment has a FSKCW radar 100 for successively receiving input of vehicle speed data Vfrom an existing vehicle speed sensor (not shown in the drawing) of avehicle and an output device 200 (such as a liquid crystal display,speakers or the like), for outputting information of the FSK CW radar100, including measured information on a target and information on theinclination of the FSK CW radar 100 for the radar mounted vehicle.

The FSK CW radar 100 has a transceiver part including a transmittingpart 110 for emitting radio waves A in the forward direction of theradar mounted vehicle and a receiving part 120 for receiving echoes Bfrom objects (a target, the track of the radar mounted vehicle) in theforward direction of the radar mounted vehicle and a control processingpart 130 for detecting an object in the forward direction of the radarmounted vehicle from output from the receiving part 120 as well as ahousing (refer to FIG. 5) accommodating these parts.

The transmitting part 110 has a modulator 111 for alternately outputtingtwo types of modulated signal in response to switchover instructionsfrom the control processing part 130, a transmitter 112 for outputtinghigh frequency signals (e.g. milliwaves) of frequencies f1 and f2emitted in correlation to the modulated signal's from the modulator 111,a transmitting antenna 113 for transmitting output signals from thetransmitter 112 as radio waves A and a directionality coupler 114 forguiding a part of the output from the transmitter 112 to the receivingpart 120 as a standard signal of frequency conversion to an intermediatefrequency band. In this configuration the transmitting part 110 causescontinuous waves A having mutually differing transmission frequencies tobe alternately emitted from the transmitting antenna 113 in the forwarddirection of the radar mounted vehicle.

The receiving part 120 has a receiving antenna 121 for receiving an echoB from an object in the forward direction of the radar mounted vehicle,a mixer 122 for generating a beat signal for each transmitted frequencyf1 and f2 of the radio waves A by mixing signals from the directionalitycoupler 114 and output signals from the receiving antenna 121, analogcircuit 123 for amplifying and demodulating output signals of the mixer122 for each of the transmitted frequencies f1 and f2 of the radio wavesA, and an A/D converter 124 for sampling analog signals F1 and F2 outputfrom the analog circuit 123 for each transmitted frequency f1 and f2 ofthe radio waves A at suitable sampling intervals.

In this configuration the receiving part 120 detects echoes B from anobject in the forward direction of the radar mounted vehicle afteramplification of the transmitted frequencies f1 and f2 of the radiowaves A.

Process control part 130 has a microcomputer connected to the outputdevice 200. By executing a program, this microcomputer runs a signalprocessing part 131 and a storage part 132 as functional configurationparts. The signal processing part 131 instructs the modulator 111 andthe analog circuit 123 on the timing of the switchover between the twotransmitted frequencies f1 and f2 and detects information onmeasurements concerning the target (the distance from the radar 100 tothe target, the relative speeds of the radar 100 and the target) andinformation on the inclination of the two frequency radar 100 from thereception part 120, before outputting this information to the outputdevice 200. Further, the storage part 132 stores in advance, fixed valuedata groups required by the signal processing part 131 for the detectionof information on the inclination of the two frequency radar 100 (lowspeed detection threshold values, two threshold values for the detectionof the two side lobes and two threshold values for detecting mountingattitude error) and stores frequency spectra obtained by the 131 ashistory information.

As shown in FIG. 5, the housing has two guards with through holes 141 adisposed on opposite sides of the housing, a securing member (not shownin the drawing) for securing the housing 141 to a holding bracket 140secured to the front part of the radar mounted vehicle and a pluralityof tightening bolts 142 that engage the corresponding tightening screwholes 140 a of the holding bracket 140 when the adjusting bolts 142 areinserted in each of the through holes of the two guards 141 a. Thishousing being so configured, a user can adjust the interval between thehousing 141 and the bracket 140 through a plurality of positions byadjusting the degree of tightening of each of the adjusting bolts 142,thereby enabling the user to adjust the attitude of the housing 141 forthe holding bracket 140, in other words to adjust the mounting attitudeof the radar for the radar mounted vehicle. The cover 141 may be securedat three points by the group of adjusting screws 142 to enable theinclination of the cover 141 to be corrected around the x-axis and they-axis, however this is not essential. For example the cover 141 can besecured in position by the group of adjusting screws 142 in four or morepoints to enable fine adjustment of the inclination of the cover 141.Further, the cover 141 can be secured in position by the group ofadjusting screws 142 along two points above the central axis of thecover following in the direction of the y-axis, to mitigate the effectsof the inclination of the cover 141 around the y-access on resultsmeasured.

The processes executed by the microcomputer of the radar 100, that is tosay, the processes run by each functioning processing part as realizedby the execution of software by the microcomputer, will now be describedincluding an explanation of the processes of adjustment performed by theuser. Here, the focus will be on the strong first side lobe a1 andsecond side lobe a2 from among the series of side lobes a1, a2, . . . onthe side of the road surface.

FIG. 6 is a flowchart depicting the processes executed by themicrocomputer of the radar 100.

As the signal control part 131 of the control processing part 130commences instructions on the timing of the switchover between the twotransmitted frequencies f1 and f2, the instructions for the timing ofthe switchover between these two transmitted frequencies are perceivedalternately and cyclically by the modulator 111 of the transmitting part110 and the analog circuit 123 of the receiving part 120 respectively.Thereafter, radio waves from each of the transmitted frequencies f1 andf2 are alternately and cyclically emitted from the transmitting antenna113 of the transmitting part 110 (Step 500) and the receiving part 120commences detecting echoes from an object existing within the range ofthe radiation of these radio waves (Step 501).

When the receiving part 120 detects an echo from an object within therange of radiation of radio waves A, the signal processing part 131 ofthe control processing part 130 decomposes into the frequency componentsof a sample signal from the receiving part 120 using Fast FourierTransformation (FFT) processes on the respective transmitted frequenciesf1 and f2 (Step 502).

The signal processing part 131 of the control processing part 130 thenreads the low speed detection threshold value from the storage part 132and compares this value with vehicle speed data V from the vehicle speedsensor (Step 503).

When the results indicate that this vehicle speed data V from thevehicle speed sensor is less than the low speed detection thresholdvalue, the signal processing part 131 of the control processing part 130returns to execute the processes of Step 502, and implements FFTprocesses on new sample signals from the receiving part 120. Here, thereason that signal processing part 131 returns to implement Step 502 ifthe vehicle speed data V from the vehicle sensor is below the low speeddetection threshold value is that when the radar mounted vehicle istraveling at low speed it is unlikely that information on theinclination of the radar 100 will be accurately detected.

When on the other hand the vehicle speed data V from the vehicle speedsensor is above the low speed detection threshold value, the signalprocessing part 131 of the control processing part 130 implements thefollowing processes to assess the relative attitude of the radar 100 forthe radar mounted vehicle.

Firstly, the signal processing part 131 of the control processing part130 makes the frequency of the frequency spectral obtained at Step 502dimensionless by dividing by the vehicle speed data V from the vehiclespeed sensor (Step 504). The signal processing part 131 of the controlprocessing part 130 then stores the frequency spectral data thefrequency of which has been made dimensionless in the storage part 132as history information, synthesizes frequency spectral data storedwithin a prescribed time (e.g. for one minute) from the present fromamong the frequency spectral data groups stored as history informationin the storage part 132 and divides that synthesized data by the numberof synthesized data (Step 505). In this way, as shown in FIG. 7, thefrequency spectra are obtained in which peak signals p1 and p2 arise inthe positions of the frequencies s1 and s2 established by the designvalues ø1 and ø2 of the angles Φ1 and Φ2 formed by the main lobe a0 andeach of the side lobes a1 and a2. In contrast to this, if the radar 100rotates from the standard attitude around a straight axis horizontal tothe forward direction of the radar mounted vehicle, as shown in FIG. 8,the frequency spectral is obtained in which peak signals p1′ and p2′arise in the positions of the frequencies s1′ and s2′ established by thesum of the angle of rotation θ of the radar 100 and the design values ø1and ø2 of the angles Φ1 and Φ2 formed by the main lobe a0 and each ofthe side lobes a1 and a2.

The signal processing part 131 of the control. processing part 130 readsthe threshold values P1 and P2 (P1>P2) for detecting the two side lobesfrom the storage part 132, and detects the peak signal existing betweenthese two side lobe detection threshold values (above P2 below P1) fromthe frequency spectral obtained at Step 505 (Step 506). Peak signalgroups including peak signals corresponding to each of the side lobes a1and a2 are detected in this way.

Thereafter, the signal processing part 131 of the control processingpart 130 reads the two threshold values for detecting mounting attitudeerror S1 and S2 (S1>S2) and decides whether or not the same number ofpeak signal frequencies exist in the frequency region (above S2 belowS1) between these two threshold values for detecting mounting attitudeerror, as the number of side lobes a1 and a2 (Step 507). If the detectedresults indicate that the same number of peak signals (2) exist betweenthe two threshold values for detecting mounting attitude error as thenumber of side lobes a1 and a2 (2), it can be assumed that the radar 100is maintaining the standard attitude for the radar mounted vehicle.

Thus, when the number of peak signals existing between the two thresholdvalues for detecting mounting attitude error (above S2 below S1) is thesame as the number of side lobes a1 and a2, that is to say, when theradar 100 is maintaining the standard attitude for the radar mountedvehicle, the signal processing part 131 of the control processing part130 calculates information measured concerning the target from the phasedifference and the peak signal frequency (Doppler frequency) correlatedto the main lobe and outputs that information to the output device 200.Practically, it reads the target detection threshold P3 from the storagepart 132, detects the peak signal (peak signal P0 in FIG. 7) above thetarget detection threshold P3 for each transmitted frequency, andcalculates information on measurements concerning the relative speeds,Rate, of the radar 100 and the target and the distance, Range, from theradar 100 to the target, from the phase difference and the frequency ofthe peak signals P0 (Step 509). Here, the expressions (6) and (7) areused for calculating this information measured concerning the target.Range=c·Δø/{4·π·Δf}  (6)Rate=c·fd/(2·fc)  (7)

Here, c is the speed of light, Δø is the phase difference (ø1−ø2) of thepeak signals of the frequency spectral obtained for each transmittedfrequency f1 and f2, Δf is the difference (f1−f2) between thetransmitted frequencies f1 and f2, fd is the average value (fd1+fd2)/2of the frequencies. fd1 and fd2 of the peak signals of each frequencyspectral obtained for each transmitted frequency f1 and f2 and fc is theaverage value (f1+f2)/2 of the transmitted frequencies f1 and f2 (thesame as the following expressions also).

Further, at this point, the signal processing part 131 of the controlprocessing part 130 may also be made to execute surface conditiondiagnosis processes based on the amplitude of peak signals existingbetween the two threshold values for detecting mounting attitude error(above S2 below S1). For example, as the amplitude of peak signalscorresponding to the side lobes a1 and a2 increases if there is ruggedon the surface, when it is below the first threshold value between thetwo threshold values for detecting mounting attitude error (above S2below S1), a warning message may be output indicating that there is suchrugged on the surface. Further, as the amplitude of peak signalscorresponding to the side lobes a1 and a2 increases if there is waterpuddle on the surface, when it is above the second threshold value(above S2 below S1) a warning message may be output indicating a cautionagainst slipping.

On the other hand, when the number of peak signals existing between thetwo threshold values for detecting mounting attitude error (above S2below S1) is not the same as the number of side lobes a1 and a2, that isto say, when the attitude of the radar 100 for the radar mounted vehiclehas varied, the signal processing part 131 of the control processingpart 130 calculates the angle θ by which the mounting attitude of theradar 100 is rotated from the standard attitude around a straight axishorizontal to the forward direction of movement of the radar mountedvehicle from the following two expressions (8) and (9).θ=cos⁻¹ {s 1′·c/(2·fc)}−ø1  (8)θ=cos⁻¹ {s 2′·c/(2·fc)}−ø2  (9)

The signal processing part 131 of the control processing part 130outputs the average value of the two angles obtained from theexpressions (8) and (9) to the output device 200 as information on theinclination of the radar 100 with respect to the radar mounted vehicle.Further, the signal processing part 131 of the control processing part130 reads a warning message from the storage part 132 indicating theneed for an adjustment of the mounting attitude of the radar and outputsthis warning message to the output device 200 together with theinformation on the inclination of the radar 100. In this way, a warningmessage indicating the need for an adjustment of the mounting attitudeof the radar 100 and information on the inclination of the radar 100with respect to the radar mounted vehicle are output from the outputdevice 200 in at least one form from among audio and visual output (Step508). The result is that through this warning message, a user is madeaware that the mounting attitude of the radar requires adjustment and isable to recognize, from the information on the inclination of the radar100 with respect to the radar mounted vehicle, the degree to which themounting attitude of the radar with respect to the radar mounted vehiclehas changed from the standard attitude. The work of adjusting themounting attitude of the radar 100 can then be smoothly performed bytightening the adjusting bolts 142.

Through the execution of the above described processes, a change in themounting attitude of the radar 100 with respect to the radar mountedvehicle can be detected without adding hardware to a FSK CW radar.

It has been described with respect to this embodiment that a userperforms the operation of adjusting the mounting attitude of the radar100 with respect to the radar mounted vehicle, however it is alsosuitable to install a motor that rotates the radar 100 around a straightaxis horizontal to the forward direction of the radar mounted vehicleand for the microcomputer to control the rotation of the motor to reducethe information on the inclination of the radar 100 with respect to theradar mounted vehicle.

Further, it has been described with respect to this embodiment that awarning message notifying a user that the mounting attitude of the radarrequires adjustment is output in at least one of either an audio orvisual form, however it is also suitable to notify a user of thisinformation through means such as output of a warning alarm or theflashing of an LED or the like.

Again, it has been described with respect to this embodiment that thefrequency of the frequency spectral is made dimensionless, however itdoes not need necessarily be achieved in this way. For example, it isalso suitable to detect the frequency of a peak signal correlated to themain lobe and to use the value for the frequency thus detected to dividethe frequency of the frequency spectral. Moreover, in a configuration inwhich processes to assess the relative attitude of the radar 100 withrespect to the radar mounted vehicle are performed only when the speedof the vehicle reaches a predetermined value, it is not necessary tomake the frequency of the frequency spectral obtained through FFTprocesses dimensionless.

Further, in the above description, the upper limit value S1 and thelower limit value S2 for the appropriate frequency region in which peaksignals correlated to the side lobes a1 and a2 may exist were fixed,however this is not essential. For example, the appropriate frequencyregion in which peak signals corresponding to the side lobes a1 and a2may exist may be changed in coordination to the frequency of peaksignals detected in the past as peak signals correlated to the sidelobes a1 and a2. The processes performed in such an arrangement aredescribed following with reference to FIG. 9, however the followingdescription covers only those points that are different to thoseprocesses described with respect to FIG. 6.

By performing same processes as described above (Steps 500-506), oncethe peak signals existing between the threshold (above P1 below P2) fordetecting the two side lobes are detected, the signal processing part131 of the control processing part 130 decides whether or not historyinformation on peak signals correlated to the side lobes a1 and a2exists in the storage part 132 (Step 510).

If the result is that such history information does not exist in thestorage part 132 the signal processing part 131 of the controlprocessing part 130 stores frequencies of peak signals detected at Step506 in the storage part as history information and, by performing thesame processes as described above, calculates information measuredconcerning the target, comprising the relative speeds of the target andthe radar 100 and the distance from the radar 100 to the target (Step509). Thereafter, the signal processing part 131 of the controlprocessing part 130 returns to Step 502 and executes FFT processes inrespect of a new sampled signal from the reception part 120.

If on the other hand, history information on peak signals correlated tothe side lobes a1 and a2 does exist in the storage part 132, the signalprocessing part 131 of the control processing part 130 calculates theaverage value of all history information and calculates the differencebetween this average value and the frequency of the peak signal obtainedat Step 511 (Step 511). The signal processing part 131 of the controlprocessing part 130 then decides whether or not the radar 100 ismaintaining the standard attitude by comparing this value for thedifference with a predetermined value (Step 512). This is equivalent tomaking a frequency range of a predetermined bandwidth the center ofwhich is the average value of the history information, the appropriatefrequency range within which peak signals correlated to the side lobesa1 and a2 exists.

If, as a result of that comparison, the value for the difference isabove the predetermined value, information on the inclination of theradar 100 for the radar mounted vehicle is calculated in the same manneras applies with respect to the above described configuration, and thatinformation is output to the output device 200 together with a warningmessage indicating that the mounting attitude of the radar requiresadjusting (Step 508). On the contrary, if that value for the differenceis below the predetermined value however, the signal processing part 131of the control processing part 130 stores the frequency of the peaksignal detected at Step 506 in the storage part as history information(Step 513) and, by performing the same processes as those describedabove for the purpose, calculates information measured concerning thetarget, comprising the relative speeds of the target and the radar 100and the distance from the radar 100 to the target (Step 509).Thereafter, the signal processing part 131 of the control processingpart 130 returns to Step 502 and executes FFT processes in respect of anew sampled signal from the reception part 120.

It has been described with respect to this embodiment that when theradar 100 is not maintaining the standard attitude, information on theinclination of the radar 100 with respect to the radar mounted vehicleis output from the output device 200, however, it is also suitable forthis information to be preserved as history information together withthe time of detection of the frequency of peak signals correlated to theside lobes, and for time-varying of the frequency of peak signalscorrelated to the side lobes to be output as time-varying of themounting attitude of the radar 100 with respect to the radar mountedvehicle.

A radar system including a FSK CW radar was provided as an embodiment ofthe present invention, however radar systems including radar having amodulation system other than a FSK CW radar can also be applied. Forexample, a radar system including an FMCW radar can also be applied. Anexample of the present invention applied using a radar system includinga homodyne type FMCW radar will now be described, detailing however,only those aspects that are different to the above descriptionconcerning the embodiment of present invention using the radar systemincluding a FSK CW radar.

An FMCW radar related to this embodiment of the present invention hasthe same hardware configuration as the above described FSK CW radar.That is to say, as shown in FIG. 4 this FMCW radar has a transmittingpart 110 for emitting radio waves in the forward direction of the radarmounted vehicle, a receiving part 120 for receiving echoes from objectsin the forward direction of the radar mounted vehicle, a controlprocessing part 130 which detects an object in the forward direction ofthe radar mounted vehicle from output from the receiving part 120, aswell as a housing (not shown in FIG. 4, refer to FIG. 5) accommodatingthese parts. In this configuration however, the processes of thetransmitting part 110, the receiving part 120 and the control processingpart 130 are different to those performed by those parts in theembodiment using the FSK CW radar as described above. Practically, thisembodiment is as follows.

At the transmitting part 110, the transmitter 112 repeatedly outputs FMmodulated high frequency signals in correlation to triangular wavesignals from the modulator 111. This causes radio waves A repeatedlymodulated with triangular waves as shown in FIG. 10, to be emitted fromthe transmitting antenna 113 of the transmitting part 110.

If an object exists in the region of radiation of the radio waves, atthe receiving part 120, firstly, the receiving antenna 113 receives anecho B from the object as shown in FIG. 10, and the mixer mixes theechoes B and radio waves A from the directionality coupler 14. In thisway, a beat signal the frequency of which alternately shows the twovalues fb+ and fb− at predetermined cycles as shown in FIG. 11 isgenerated. These beat signals are sampled at determined samplingintervals T by an A/D converter after being demodulated and amplified atan analog circuit 123 at each half cycle of those repeated cycles.

At the control processing part 130, the signal processing part 131instructs the modulator 112 and the analog circuit 123 on the timing forthe folding of the triangular waves, and executes processes to detectinformation on measurements concerning the target, including thedistance from the radar 100 to the target and relative speeds of theradar 100 and the target. In this way the processes depicted in theflowchart of FIG. 13 or the flowchart of FIG. 14 are executed; theseprocesses being different from those illustrated in the flowcharts shownin FIGS. 6 and 9 in the following respects.

The FFT processing Step 502′ of the flowcharts shown in FIGS. 13 and 14differs from the FFT processing Step 502 of the flowcharts shown inFIGS. 6 and 9 in the respect that sampled signals from the receivingpart 110 decompose into frequency components for each half cycle of therepeated cycles of the beat signals. The frequency spectral obtained byFFT processing Step 502′ in the flowcharts of FIGS. 13 and 14 is shownin FIG. 12. In one frequency spectral among the frequency spectraobtained for each half cycle of the cycles of repeated beat signals, apeak signal arises respectively in one frequency f1 b+ among thefrequencies alternately shown by the beat signals from the echoes fromthe first side lobe a1 and in one frequency f2 b+ among the frequenciesalternately shown by the beat signals of the echoes from the second sidelobe a2. Further, in the other frequency spectral (not shown in thedrawings), a peak signal arises respectively in the other frequency f1b− among the frequencies alternately shown by the beat signals of theechoes from the first side lobe a1 and in the other frequency f2 b−among the frequencies alternately shown by the beat signals of theechoes from the second side lobe a2.

Moreover, the flowcharts shown in FIGS. 13 and 14 differ from thoseshown in FIGS. 6 and 9 in not including the branch process for vehiclespeed at Step 503 and the process for making the frequencydimensionless, Step 504, by dividing the frequency by the vehicle speeddata. The reason for these differences is that a frequency of afrequency spectral obtained by FFT processes of an FMCW radar does notchange in correlation with vehicle speed.

Again, the target detection process 504′ of the flowcharts shown inFIGS. 13 and 14 differs from the target detection process 504 of theflowcharts shown in FIGS. 6 and 9 in using the following expressions(10) and (11) for calculation information concerning the target.Range=c·(fb++fb−)/(8·ΔF·fm)  (10)Rate=λ·(fb+−fb−)/4  (11)

Here, fm is the cycle of repetition of the triangular waves, ΔF is thebandwidth of the frequency deviation of FM, λ is the wavelength of radiowaves from the transmitting antenna and fb+ and fb− are frequenciesshown by peak signals correlated to the main lobe.

Further, the processes for issuing a warning about an error of themounting attitude of the radar, Step 508′ in the flowcharts shown inFIGS. 13 and 14, differs from the processes for issuing a warning aboutan error of the mounting attitude of the radar of Step 508 in theflowcharts shown in FIGS. 6 and 9 in using the following expressions(12) and (13) to calculate the attitude of the inclination of the targetfor the radar mounted vehicle.θ=sin⁻¹ {(H/(f 1 b++f 1 b−)·(8·ΔF·fm/c)}−ø1  (12)θ=sin⁻¹ {(H/(f 2 b++f 2 b−)·(8·ΔF·fm/c)}−ø2  (13)

Here, H is the distance (H of FIG. 2) from the surface to the main lobewhen the radar is maintaining the standard attitude, f1 b+ and f1 b− arethe frequency of the peak signal correlated to the first side lobe a1and the frequency of the peak signal correlated to the second side lobea2.

The examples above were described envisaging a rolling car type vehicleas the vehicle on which the radar is mounted, however the above radarsystems may also be mounted on a two wheeled vehicle or other type ofmoving body.

Further, in the above descriptions, there are two side lobesconcentrated however it is also suitable to have one side lobe.Moreover, three or more side lobes can be used where it is possible todetect beat signals correlated to a still greater number of side lobes.

INDUSTRIAL APPLICABILITY

As described, a radar device related to the present invention enablesdetection of changes of mounting attitude for a moving body withoutrequiring additional hardware.

1. A radar device mounted on a moving object moving along a continuousplane comprising: a transceiver unit which transmits a signal having amain lobe in a direction of movement of said moving object and a sidelobe directed toward said continuous plane and for receiving a firstreflection signal from a target in a direction of said main lobe and asecond reflection signal from said continuous plane in a direction ofsaid side lobe; and control processing means which detects a frequencyof a beat signal of said second reflection signal received by saidtransceiver unit and a signal emitted by said transceiver unit and fordetecting information correlated to the relative attitude of said radardevice for said continuous plane based on said frequency.
 2. A radardevice mounted on a moving object moving along a continuous planecomprising: a transceiver unit which transmits a signal having a mainlobe in a direction of movement of said moving object and a side lobedirected toward said continuous plane and for receiving a firstreflection signal from a target in a direction of said main lobe and asecond reflection signal from said continuous plane in a direction ofsaid side lobe; and control processing means which detects a frequencyof a beat signal of said second reflection signal received by saidtransceiver unit and a signal emitted by said transceiver unit anddetects changes in an attitude of said radar device for said continuousplane based on said frequency.
 3. A radar device according to either ofclaims 1 or 2, wherein said control processing means detects a surfacecondition of said continuous plane based on the strength of a beatsignal of said second reflection signal received by said transceiverunit and the signal emitted by said transceiver unit.
 4. A radar systemmounted on a moving object moving along a continuous plane comprising:said radar device of claim 1; and output means which outputs a resultdetected by said control processing means as information showing anattitude of said radar for said moving object.
 5. A radar system mountedon a moving object moving along a continuous plane comprising: saidradar device of claim 2; and output means which notifies a change in anattitude of said radar device for said moving object when said controlprocessing means detects a change in mounting attitude of said radardevice for said continuous plane.
 6. A radar system mounted on a movingobject moving along a continuous plane comprising: said radar device ofclaim 3; and output means which outputs a notification of a surfacecondition of said continuous plane detected by said control processingmeans.